Three people who had COVID-19 and were deemed to be free of the virus have restested positive.
Victorian Health Minister Martin Foley said they were not deemed fresh cases and were not included in Wednesday’s official coronavirus numbers.
Two cases were in metropolitan Melbourne, with health authorities determining they were shedding traces of virus from their previous infections.
While a third case was a woman who returned home to South Australia from Victoria and whose case is currently under review.
“So, in an abundance of caution, both jurisdictions have decided to align their public health advice this morning,” Mr Foley told reporters on Wednesday morning.
“This means that the top of health risk potential exposure sites are at both the Melbourne Central and Melbourne Airport.”
An alert will also be issued at Adelaide Airport.
Anyone with symptoms or who visited Melbourne Central between 2-5pm on November 8 or Terminal 4 at Melbourne Airport between 12-1pm on the same day are being urged to get tested as a precaution.
Two people sitting next to the woman on the Jetstar flight JQ776 on November 9 are also in hotel quarantine in South Australia, while another two, considered casual contacts, will undertake home quarantine.
SA Health’s Chief Public Health Officer Nicola Spurrier said more testing was underway to determine if the positive result represented an old or rare re-infection.
She said it could take a few days for an outcome.
“We are treating this as an infectious case in SA and so is Victoria until we get more information,” Prof. Spurrier said.
“It’s too early to tell if it is (a re-infection). Shedding is a much more common event than re-infection, so in terms of probability it is likely to be part of that old infection but… we are taking an abundance of caution.”
Prof. Spurrier said there was no risk to the South Australian public and the woman in her 20s followed all the right protocols.
The woman, who worked in aged care in Victoria, was first diagnosed with the virus back in August and was later cleared of the infection.
Department of Health and Human Services testing commander Jeroen Weimar previously explained people could continue to shed traces of coronavirus even after the 14-day quarantine period.
“Those are not judged to be infectious,” he said.
“They present no risk to the wider community, there’s no risk of onward transmission, but they’re still shedding traces of the virus, and we’re picking this up in areas like sewage testing and, of course, sometimes even when we’re doing repeat nasal swabs, we still pick up possible traces.”
Victoria recorded its 12th straight day of zero new coronavirus cases on Wednesday.
There is just one case with an unknown source and four active cases across the state.
In SA, the woman’s infection has brought the state’s total number of cases to 519 with 17 now active; all of which are in hotel quarantine.